Human parainfluenza viruses (HPIVs) are important pathogens in human populations, causing severe lower respiratory tract infections in infants and young children. HPIV1 and HPIV2 are the principal etiologic agents of laryngotracheobronchitis (croup), and can also cause pneumonia and bronchiolitis (Collins et al., 3rd ed. In “Fields Virology,” B. N. Fields, D. M. Knipe, P. M. Howley, R. M. Chanock, J. L. Melnick, T. P. Monath, B. Roizman, and S. E. Straus, Eds., Vol. 1, pp. 1205-1243. Lippincott-Raven Publishers, Philadelphia, 1996). HPIV3 ranks second after respiratory syncytial virus (RSV) as a leading cause of hospitalization for viral lower respiratory tract disease in infants and young children (Collins et al., 3rd ed. In “Fields Virology,” B. N. Fields, D. M. Knipe, P. M. Howley, R. M. Chanock, J. L. Melnick, T. P. Monath, B. Roizman, and S. E. Straus, Eds., Vol. 1, pp. 1205-1243. Lippincott-Raven Publishers, Philadelphia, 1996; Crowe et al., Vaccine 13:415-421, 1995; Marx et al., J. Infect. Dis. 176:1423-1427, 1997).
PIVs are also important causes of respiratory tract disease in adults. Collectively, HPIV1, HPIV2, and HPIV3 have been identified through a 20 year study as responsible etiologic agents for approximately 18% of hospitalizations for pediatric respiratory tract disease (Murphy et al., Virus Res. 11:1-15, 1988). HPIVs have also been implicated in a significant proportion of cases of virally-induced middle ear effusions in children with otitis media (Heikkinen et al., N. Engl. J. Med. 340:260-4, 1999).
Despite considerable efforts to develop effective immunogenic compositions against HPIVs, no vaccines have yet been approved for any HPIV serotype, nor for ameliorating HPIV related illnesses. The most promising prospects to date are live attenuated vaccine viruses since these have been shown to be efficacious in non-human primates even in the presence of passively transferred antibodies, an experimental situation that simulates that present in the very young infant who possesses maternally acquired antibodies (Crowe et al., Vaccine 13:847-855, 1995; Durbin et al., J. Infect. Dis. 179:1345-1351, 1999). Two live attenuated PIV3 vaccine candidates, a temperature-sensitive (ts) derivative of the wild-type PIV3 JS strain (designated PIV3 cp45) and a bovine PIV3 (BPIV3) strain, are undergoing clinical evaluation (Karron et al., Pediatr. Infect. Dis. J. 15:650-654, 1996; Karron et al., J. Infect. Dis. 171:1107-1114, 1995a; Karron et al., J. Infect. Dis. 172, 1445-1450, 1995b). The live attenuated PIV3 cp45 vaccine candidate was derived from the JS strain of HPIV3 via serial passage in cell culture at low temperature and has been found to be protective against HPIV3 challenge in experimental animals and to be satisfactorily attenuated, genetically stable, and immunogenic in seronegative human infants and children (Belshe et al, J. Med. Virol. 10:235-242, 1982; Belshe et al., Infect. Immun. 37:160-5, 1982; Clements et al., J. Clin. Microbiol. 29:1175-82, 1991; Crookshanks et al., J. Med. Virol. 13:243-9, 1984; Hall et al., Virus Res. 22:173-184, 1992; Karron et al., J. Infect. Dis. 172:1445-1450, 1995b). Because these PIV3 candidate viruses for use in vaccines are biologically derived, there are no proven methods for adjusting the level of attenuation should this be found necessary from ongoing clinical trials.
To facilitate development of PIV vaccines, recombinant DNA technology has recently made it possible to recover infectious negative-stranded RNA viruses from cDNA (for reviews, see Conzelmann, J. Gen. Virol. 77:381-89, 1996; Palese et al., Proc. Natl. Acad. Sci. U.S.A. 93:11354-58, 1996). In this context, recombinant rescue of infectious virus has been reported for respiratory syncytial virus (RSV), rabies virus (RaV), canine distemper virus, mumps virus, infectious hematopoietic necrosis virus, simian virus 5 (SV5), rinderpest virus, Newcastle disease virus (NDV), vesicular stomatitis virus (VSV), measles virus (MeV), and Sendai virus (murine parainfluenza virus type 1 (MPIV1)) from cDNA-encoded genomic or antigenomic RNA in the presence of essential viral proteins (see, e.g., Garcin et al., EMBO J. 14:6087-6094, 1995; Lawson et al., Proc. Natl. Acad. Sci. U.S.A. 92:4477-81, 1995; Radecke et al., EMBO J. 14:5773-5784, 1995; Schnell et al., EMBO J. 13:4195-203, 1994; Whelan et al., Proc. Natl. Acad. Sci. U.S.A. 92:8388-92, 1995; Hoffman et al., J. Virol. 71:4272-4277, 1997; Kato et al., Genes to Cells 1:569-579, 1996, Roberts et al., Virology 247:1-6, 1998; Baron et al., J. Virol. 71:1265-1271, 1997; International Publication No. WO 97/06270; Collins et al., Proc. Natl. Acad. Sci. U.S.A. 92:11563-11567, 1995; Clarke et al., J. Virol. 74:4831-4838, 2000; Biacchesi et al., J. Virol. 74:11247-11253, 2000; Gassen et al., J. Virol. 74:10737-10744, 2000; U.S. patent application Ser. No. 08/892,403, filed Jul. 15, 1997 (corresponding to published International Application No. WO 98/02530 and priority U.S. Provisional Application No. 60/047,634, filed May 23, 1997, 60/046,141, filed May 9, 1997, and 60/021,773, filed Jul. 15, 1996); U.S. patent application Ser. No. 09/291,894, filed on Apr. 13, 1999; International Application No. PCT/US00/09695, filed Apr. 12, 2000 (which claims priority to U.S. Provisional Patent Application Ser. No. 60/129,006, filed Apr. 13, 1999); International Application No. PCT/US00/17755, filed Jun. 23, 2000 (which claims priority to U.S. Provisional Patent Application Ser. No. 60/143,132, filed by Bucholz et al. on Jul. 9, 1999); Juhasz et al., J. Virol. 71:5814-5819, 1997; He et al. Virology 237:249-260, 1997; Peters et al. J. Virol. 73:5001-5009, 1999; Baron et al. J. Virol. 71:1265-1271, 1997; Whitehead et al., Virology 247:232-9, 1998a; Whitehead et al., J. Virol. 72:4467-4471, 1998b; Jin et al. Virology 251:206-214, 1998; Bucholz et al. J. Virol. 73:251-259, 1999; and Whitehead et al., J. Virol. 73:3438-3442, 1999, each incorporated herein by reference in its entirety for all purposes).
Additional publications in the field of the invention report successful recovery of recombinant parainflunza viruses (PIVs), specifically HPIV2, HPIV3, and BPIV3 (see, e.g., Durbin et al., Virology 235:323-332, 1997; Schmidt et al., J. Virol. 74:8922-8929, 2000; Kawano et al., Virology 284:99-112, 2001; U.S. patent application Ser. No. 09/083,793, filed May 22, 1998 (corresponding to U.S. Provisional Application No. 60/059,385, filed Sep. 19, 1997); U.S. Provisional Application No. 60/412,053, filed Sep. 18, 2002; and U.S. Provisional Application No. 60/047,575, filed May 23, 1997 (corresponding to International Publication No. WO 98/53078), each incorporated herein by reference). These reports further address genetic manipulation of viral cDNA clones to determine the genetic basis of phenotypic changes in biological mutants, for example, which mutations in a biological mutant HPIV3 (JS cp45) virus specify its ts, ca and att phenotypes, and which gene(s) or genome segment(s) of BPIV specify its attenuation phenotype. Additionally, these and related publications discuss construction of novel PIV vaccine candidates having a wide range of different mutations, as well as methods for evaluating the level of attenuation, immunogenicity and phenotypic stability exhibited by such recombinant vaccine candidates (see also, U.S. application Ser. No. 09/586,479, filed Jun. 1, 2000 (corresponding to U.S. Provisional Patent Application Ser. No. 60/143,134, filed on Jul. 9, 1999); and U.S. patent application Ser. No. 09/350,821, filed by Durbin et al. on Jul. 9, 1999, each incorporated herein by reference).
Thus, infectious wild-type recombinant PIV3, (r)PIV3, as well as a number of ts and other modified derivatives, have now been recovered from cDNA. Reverse genetics systems have been used to generate infectious virus bearing defined mutations that specify attenuation and other desirable phenotypes, and to study the genetic basis of attenuation and other phenotypic changes in existing vaccine candidate viruses. For example, the three amino acid substitutions found in the L gene of cp45, singularly or in combination, have been found to specify the ts and attenuation phenotypes. Additional ts and other attenuating mutations can be introduced in other regions of the PIV3cp45 genome.
In addition, a chimeric PIV1 vaccine candidate has been generated using the PIV3 cDNA rescue system by replacing the PIV3 HN and F open reading frames (ORFs) with those of PIV1 in a PIV3 full-length cDNA, that optionally contains selected attenuating mutations. Exemplary recombinant chimeric viruses derived from these cDNA-based methods include a HPIV3-1 recombinant bearing all three identified mutations in the L gene, rPIV3-1.cp45L (Skiadopoulos et al., J. Virol. 72:1762-8, 1998; Tao et al., J. Virol. 72:2955-2961, 1998; Tao et al., Vaccine 17:1100-1108, 1999, incorporated herein by reference). rPIV3-1.cp45L was attenuated in hamsters and induced a high level of resistance to challenge with PIV. Yet another recombinant chimeric virus, designated rPIV3-1.cp45, has been produced that contains 12 of the 15 cp45 mutations, i.e., excluding the mutations that occur in HN and F. This recombinant vaccine candidate is highly attenuated in the upper and lower respiratory tract of hamsters and induces a high level of protection against HPIV1 infection (Skiadopoulos et al., Vaccine 18:503-510, 1999). However, for use against HPIV1, the immunogenicity of chimeric HPIV3-1 vaccine candidates against HPIV1 challenge is dampened in hosts that exhibit immune recognition of HPIV3.
Recently, a number of studies have focused on the possible use of viral vectors to express foreign antigens toward the goal of developing vaccines against a pathogen for which other vaccine alternatives are not proved successful. In this context, a number of reports suggest that foreign genes may be successfully inserted into a recombinant negative strand RNA virus genome or antigenome with varying effects (Bukreyev et al., J. Virol. 70:6634-41, 1996; Bukreyev et al., Proc. Natl. Acad. Sci. U.S.A. 96:2367-72, 1999; Finke et al. J. Virol. 71:7281-8, 1997; Hasan et al., J. Gen. Virol. 78:2813-20, 1997; He et al., Virology 237:249-60, 1997; Jin et al., Virology 251:206-14, 1998; Johnson et al., J. Virol. 71:5060-8, 1997; Kahn et al., Virology 254:81-91, 1999; Kretzschmar et al., J. Virol. 71:5982-9, 1997; Mebatsion et al., Proc. Natl. Acad. Sci. U.S.A. 93:7310-4, 1996; Moriya et al., FEBS Lett. 425:105-11, 1998; Roberts et al., J. Virol. 73:3723-32, 1999; Roberts et al., J. Virol. 72:4704-11, 1998; Roberts et al., Virology 247:1-6, 1998; Sakai et al., FEBS Lett. 456:221-226, 1999; Schnell et al., Proc. Natl. Acad. Sci. U.S.A. 93:11359-65, 1996a; Schnell et al., J. Virol. 70:2318-23, 1996b; Schnell et al., Cell 90:849-57, 1997; Singh et al., J. Gen. Virol. 80:101-6, 1999; Singh et al., J. Virol. 73:4823-8, 1999; Spielhofer et al., J. Virol. 72:2150-9, 1998; Yu et al., Genes to Cells 2:457-66 et al., 1999; Duprex et al., J. Virol. 74:7972-7979, 2000; Subash et al., J. Virol. 74:9039-9047, 2000; Krishnamurthy et al., Virology 278:168-182, 2000; Rose et al., J. Virol. 74:10903-10910, 2000; Tao et al., J. Virol. 74:6448-6458, 2000; McGettigan et al., J. Virol. 75:8724-8732, 2001; McGettigan et al., J. Virol. 75:4430-4434, 2001; Kahn et al., J. Virol. 75:11079-11087, 2001; Stope et al., J. Virol. 75:9367-9377, 2001; Huang et al., J. Gen. Virol. 82:1729-1736, 2001; Skiadopoulos et al., J. Virol. 75:10498-10504, 2001; Bukreyev et al., J. Virol. 75:12128-12140, 2001; U.S. patent application Ser. No. 09/614,285, filed Jul. 12, 2000 (corresponding to U.S. Provisional Patent Application Serial No. 60/143,425, filed on Jul. 13, 1999), each incorporated herein by reference). When inserted into the viral genome under the control of viral transcription gene-start and gene-end signals, the foreign gene may be transcribed as a separate mRNA and yield significant protein expression. Surprisingly, in some cases foreign sequence has been reported to be stable and capable of expressing functional protein during numerous passages in vitro.
In order to successfully develop vectors for vaccine use, however, it is insufficient to simply demonstrate a high, stable level of protein expression. For example, this has been possible since the early-to-mid 1980s with recombinant vaccinia viruses and adenoviruses, and yet these vectors have proven to be disappointing tools for developing vaccines for human use. Similarly, most nonsegmented negative strand viruses that have been developed as vectors have not been shown to be amenable for human vaccine use. Examples in this context include vesicular stomatitis virus, an ungulate pathogen with no history of administration to humans except for a few laboratory accidents; Sendai virus, a mouse pathogen with no history of administration to humans; simian virus 5, a canine pathogen with no history of administration to humans; and an attenuated strain of measles virus which must be administered systemically and would be neutralized by measles-specific antibodies present in nearly all humans due to maternal antibodies and widespread use of a licensed measles vaccine. Furthermore, some of these prior vector candidates have adverse effects, such as immunosupression, which are directly inconsistent with their use as vectors. Thus, one must identify vectors whose growth characteristics, tropisms, and other biological properties make them appropriate as vectors for human use. It is further necessary to develop a viable immunization strategy, including efficacious timing and route of administration.
Proposed mononegaviruses for use as vaccine vectors include measles, mumps, VSV, and rabies viruses. Each of these virues have serious limitations relating to their potential use as vaccine vectors. For example, measles virus has been considered for use a vector for the protective antigen of hepatitis B virus (Singh et al., J. Virol. 73:4823-8, 1999). However, this combined measles virus-hepatitis B virus vaccine candidate could only be administered after nine months of age, on a schedule comparable to the indicated schedule for the licensed measles virus vaccine, whereas the current hepatitis B virus vaccine is recommended for use in early infancy. This is because the currently licensed measles vaccine is administered parenterally and is sensitive to neutralization and immunosuppression by maternal antibodies, and therefore is not effective if administered before 9-15 months of age. Thus, measles virus is a poor vector for antigens of pathogenic agents that cause disease in early infancy, such as RSV and the HPIVs.
The attenuated measles virus vaccine has been associated with altered immune responses and excess mortality when administered at increased dosages, which may be due at least in part to virus-induced immunosuppression and indicates that even an attenuated measles virus may not be suitable for vaccine vector use. Furthermore, the use of measles virus as a vector would be inconsistent with the global effort to eradicate this pathogen. Indeed, for these reasons it would be desirable to end the use of live measles virus and replace the present measles virus vaccine with a suitable non-measles vector that expresses measles virus protective antigens.
Rabies virus, a rare cause of infection of humans, has been considered for use as a vector (Mebatsion et al., Proc. Natl. Acad. Sci. USA 93:7310-4, 1996), but it is unlikely that a virus that is so highly fatal as rabies for humans could be developed for use as a live attenuated virus vector. Moreover, immunity to the rabies virus, which is not a ubiquitous human pathogen, is not needed for the general population, whereas more desirable vectors should be capable of eliciting a multi specific immune response against both the vector virus and the pathogen for which the vector is used as a carrier of antigenic determinants. While mumps and measles viruses are less pathogenic than the rabies virus, infection by either of these other vector candidates can yield undesirable results. Mumps virus infects the parotid gland and can spread to the testes, sometimes resulting in sterility. Measles virus establishes a viremia with widespread infection and associated rash. Mild encephalitis during mumps and measles infection is not uncommon. Measles virus is also associated with a rare progressive fatal neurological disease called subacute sclerosing encephalitis.
In contrast to such vector candidates as rabies, measles and mumps, PIV infection and disease is typically more limited, in part by confinement of infection to the respiratory tract. Viremia and spread to secondary sites can occur in severely immunocompromised subjects, but this is not a typical effect of PIV infection. Acute respiratory tract disease is the only disease associated with PIVs. Thus, the use of PIVs as vectors will, on the basis of their biological characteristics, avoid complications such as interaction of virus with peripheral lymphocytes, leading to immunosuppression, or infection of secondary organs such as the testes or central nervous system, leading to other complications. These characteristics also render PIV a better vector candidate for successful immunization, which can be achieved more easily and effectively via alternate routes, such as direct administration to the respiratory tract, compared to immunization with vectors that require parental administration.
Among a host of human pathogens for which a vector-based vaccine approach may be desirable is the measles virus. A live attenuated vaccine has been available for more than three decades and has been largely successful in eradicating measles disease in the United States. However, the World Health Organization estimates that more than 45 million cases of measles still occur annually, particularly in developing countries, and the virus contributes to approximately one million deaths per year.
Measles virus is a member of the Morbillivirus genus of the Paramyxoviridae family (Griffin et al., In “Fields Virology”, B. N. Fields, D. M. Knipe, P. M. Howley, R. M. Chanock, J. L. Melnick, T. P. Monath, B. Roizman, and S. E. Straus, Eds., Vol. 1, pp. 1267-1312. Lippincott-Raven Publishers, Philadelphia, 1996). It is one of the most contagious infectious agents known to man and is transmitted from person to person via the respiratory route (Griffin et al., In “Fields Virology”, B. N. Fields, D. M. Knipe, P. M. Howley, R. M. Chanock, J. L. Melnick, T. P. Monath, B. Roizman, and S. E. Straus, Eds., Vol. 1, pp. 1267-1312. Lippincott-Raven Publishers, Philadelphia, 1996). The measles virus has a complex pathogenesis, involving replication in both the respiratory tract and various systemic sites (Griffin et al., In “Fields Virology”, B. N. Fields, D. M. Knipe, P. M. Howley, R. M. Chanock, J. L. Melnick, T. P. Monath, B. Roizman, and S. E. Straus, Eds., Vol. 1, pp. 1267-1312. Lippincott-Raven Publishers, Philadelphia, 1996). Measles virus is discussed here as an exemplary pathogen for which a live attenuated vector vaccine is particularly desired. For reasons discussed in further detail herein below, a measles vaccine based on a recombinant HPIV1 vector system would satisfy a long-felt need in the art and fulfill an urgent need for additional effective vector systems to generate vaccines against other pathogens as well.
Although both mucosal IgA and serum IgG measles virus-specific antibodies can participate in the control of measles virus, the absence of measles virus disease in very young infants possessing maternally-acquired measles virus-specific antibodies identifies serum antibodies as a major mediator of resistance to disease (Griffin et al., In “Fields Virology”, B. N. Fields, D. M. Knipe, P. M. Howley, R. M. Chanock, J. L. Melnick, T. P. Monath, B. Roizman, and S. E. Straus, Eds., Vol. 1, pp. 1267-1312. Lippincott-Raven Publishers, Philadelphia, 1996). The two measles virus glycoproteins, the hemagglutinin (HA) and fusion (F) proteins, are the major neutralization and protective antigens (Griffin et al., In “Fields Virology”, B. N. Fields, D. M. Knipe, P. M. Howley, R. M. Chanock, J. L. Melnick, T. P. Monath, B. Roizman, and S. E. Straus, Eds., Vol. 1, pp. 1267-1312. Lippincott-Raven Publishers, Philadelphia, 1996).
The currently available live attenuated measles vaccine is administered by a parenteral route (Griffin et al., In “Fields Virology”, B. N. Fields, D. M. Knipe, P. M. Howley, R. M. Chanock, J. L. Melnick, T. P. Monath, B. Roizman, and S. E. Straus, Eds., Vol. 1, pp. 1267-1312. Lippincott-Raven Publishers, Philadelphia, 1996). Both the wild-type measles virus and the vaccine virus are very readily neutralized by antibodies, and the measles virus vaccine is rendered non-infectious by even very low levels of maternally-acquired measles virus-specific neutralizing antibodies (Halsey et al., N. Engl. J. Med. 313:544-9, 1985; Osterhaus et al., Vaccine 16:1479-81, 1998). Thus, the vaccine virus is not given until the passively-acquired maternal antibodies have decreased to undetectable levels. In the United States, measles virus vaccine is not given until 12 to 15 months of age, a time when almost all children are readily infected with the measles virus vaccine.
As noted above, measles virus continues to exact a heavy toll of mortality in developing countries, especially in children within the latter half of the first year of life (Gellin et al., J. Infect. Dis. 170:S3-14, 1994; Taylor et al., Am. J. Epidemiol. 127:788-94, 1988). This occurs because the measles virus, which is highly prevalent in these regions, is able to infect that subset of infants in whom maternally-acquired measles virus-specific antibody levels have decreased to a non-protective level. Therefore, there is a need for a measles virus vaccine that is able to induce a protective immune response even in the presence of measles virus neutralizing antibodies—with the goal of eliminating measles virus disease occurring within the first year of life as well as that which occurs thereafter. Given this need, there have been numerous attempts to develop an immunization strategy to protect infants in the latter half of the first year of life against measles virus, but none of these strategies has been effective to date.
The first strategy for developing an early measles vaccine involved administration of the licensed live attenuated measles virus vaccine to infants about six months of age by one of the following two methods (Cutts et al., Biologicals 25:323-38, 1997). In one general protocol, the live attenuated measles virus was administered intranasally by drops (Black et al., New Eng. J. Med. 263:165-169; 1960; Kok et al., Trans. R. Soc. Trop. Med. Hvg. 77:171-6, 1983; Simasathien et al., Vaccine 15:329-34, 1997) or into the lower respiratory tract by aerosol (Sabin et al., J. Infect. Dis. 152:1231-7, 1985), to initiate an infection of the respiratory tract. In a second protocol, the measles virus was given parenterally but at a higher dose than that employed for the current vaccine. The administration of vaccines that can replicate on mucosal surfaces has been successfully achieved in early infancy for both live attenuated poliovirus and rotavirus vaccines (Melnick et al., In “Fields Virology”, B. N. Fields, D. M. Knipe, P. M. Howley, R. M. Chanock, J. L. Melnick, T. P. Monath, B. Roizman, and S. E. Straus, Eds., Vol. 1, pp. 655-712. 2 vols. Lippencott-Raven Publishers, Philadelphia, 1996; Perez-Schael et al., N. Engl. J. Med. 337:1181-7, 1997), presumably because passively-acquired IgG antibodies have less access to mucosal surfaces than they do to systemic sites of viral replication. In this situation, the live attenuated poliovirus vaccine viruses are able to infect the mucosal surface of the gastrointestinal tract or the respiratory tract of young infants, including those with maternal antibodies, resulting in the induction of a protective immune response.
Therefore, a plausible method for measles immunization is to administer a live attenuated measles virus vaccine to the respiratory tract of the young infant, since this is the natural route of infection for the measles virus. However, the live attenuated measles virus that is infectious by the parenteral route was inconsistently infectious by the intranasal route (Black et al., New Eng. J. Med. 263:165-169, 1960; Cutts et al., Biologicals 25:323-38, 1997; Kok et al., Trans. R. Soc. Trop. Med. Hyg. 77:171-6, 1983; Simasathien et al., Vaccine 15:329-34, 1997), and this decreased infectivity was especially apparent for the Schwartz stain of measles virus vaccine which is the current vaccine strain. Presumably, during the attenuation of this virus by passage in tissue culture cells of avian origin, the virus lost a significant amount of infectivity for the upper respiratory tract of humans. Indeed, a hallmark of measles virus biology is that the virus undergoes rapid changes in biological properties when grown in vitro. Since this relatively simple route of immunization was not successful, a second approach was tried involving administration of the live virus vaccine by aerosol into the lower respiratory tract (Cutts et al., Biologicals 25:323-38, 1997; Sabin et al., J. Infect. Dis. 152:1231-7, 1985).
Infection of young infants by aerosol administration of measles virus vaccine was accomplished in highly controlled experimental studies, but it has not been possible to reproducibly deliver a live attenuated measles virus vaccine in field settings by aerosol to the young infant (Cutts et al., Biologicals 25:323-38, 1997). In another attempt to immunize six-month old infants, the measles vaccine virus was administered parenterally at a 10- to 100-fold increased dose (Markowitz et al., N. Engl. J. Med. 322:580-7, 1990). Although high-titer live measles vaccination improved seroconversion in infants 4-6 months of age, there was an associated increase in mortality in the high-titer vaccine recipients later in infancy (Gellin et al., J. Infect. Dis. 170:S3-14, 1994; Holt et al., J. Infect. Dis. 168:1087-96, 1993; Markowitz et al., N. Engl. J. Med. 322:580-7, 1990) and this approach to immunization has been abandoned.
A second strategy previously explored for a measles virus vaccine was the use of a formalin inactivated whole measles virus or a subunit virus vaccine prepared from measles virus (Griffin et al., In “Fields Virology”, B. N. Fields, D. M. Knipe, P. M. Howley, R. M. Chanock, J. L. Melnick, T. P. Monath, B. Roizman, and S. E. Straus, Eds., Vol. 1, pp. 1267-1312. Lippincott-Raven Publishers, Philadelphia, 1996). However, the clinical use of these vaccines in the 1960's revealed a very serious complication, namely, that the inactivated virus vaccines potentiated disease rather than prevented it (Fulginiti et al., JAMA 202:1075-80, 1967). This was first observed with formalin-inactivated measles virus vaccine (Fulginiti et al., JAMA 202:1075-80, 1967). Initially, this vaccine prevented measles, but after several years vaccinees lost their resistance to infection. When subsequently infected with naturally circulating measles virus, the vaccinees developed an a typical illness with accentuated systemic symptoms and pneumonia (Fulginiti et al., JAMA 202:1075-80, 1967; Nader et al., J. Pediatr. 72:22-8, 1968; Rauh et al., Am. J. Dis. Child 109:232-7, 1965). Retrospective analysis showed that formalin inactivation destroyed the ability of the measles fusion (F) protein to induce hemolysis-inhibiting antibodies, but it did not destroy the ability of the HA (hemagglutinin or attachment) protein to induce neutralizing antibodies (Norrby et al., J. Infect. Dis. 132:262-9, 1975; Norrby et al., Infect. Immun. 11:231-9, 1975). When the immunity induced by the HA protein had waned sufficiently to permit extensive infection with wild-type measles virus, an altered and sometimes more severe disease was seen at the sites of measles virus replication (Bellanti, Pediatrics 48:715-29, 1971; Buser, N. Engl. J. Med. 277:250-1, 1967). This a typical disease is believed to be mediated in part by an altered cell-mediated immune response in which Th-2 cells were preferentially induced leading to heightened disease manifestations at the sites of viral replication (Polack et al., Nat. Med. 5:629-34, 1999). Because of this experience with nonliving measles virus vaccines and also because the immunogenicity of such parenterally-administered vaccines can be decreased by passively-transferred antibodies, there has been considerable reluctance to evaluate such vaccines in human infants. It should be noted that disease potentiation appears to be associated only with killed vaccines.
An alternative approach to development of a vaccine vector for measles employed a replication-competent vesicular stomatitis virus (VSV), a rhabdovirus which naturally infects cattle but not humans, expressing the measles virus HA protein. This vector candidate virus was shown to replicate in the respiratory tract of animal hosts (Roberts et al., J. Virol. 73:3723-32, 1999; Schnell et al., Proc. Natl. Acad. Sci. U.S.A. 93:11359-65, 1996a). However, since VSV is an animal virus that can cause disease in humans, development of this recombinant vector for use in humans will first require that a VSV backbone that is satisfactorily attenuated in human infants be first identified (Roberts et al., J. Virol. 73:3723-32, 1999).
Yet another strategy that has been explored for developing a vaccine against measles for use in young infants has been the use of viral vectors to express a protective antigen of the measles virus (Drillien et al., Proc. Natl. Acad. Sci. U.S.A. 85:1252-6, 1988; Fooks et al., J. Gen. Virol. 79:1027-31, 1998; Schnell et al., Proc. Natl. Acad. Sci. U.S.A. 93:11359-65, 1996a; Taylor et al., Virology 187:321-8, 1992; Wild et al., Vaccine 8:441-2, 1990; Wild et al., J. Gen. Virol. 73:359-67, 1992). A variety of vectors have been explored including pox viruses, such as the replication-competent vaccinia virus or the replication-defective modified vaccinia virus Ankara (MVA) stain. Replication-competent vaccinia recombinants expressing the F or HA glycoprotein of measles virus were efficacious in immunologically naive vaccinees. However, when they were administered parenterally in the presence of passive antibody against measles virus, their immunogenicity and protective efficacy was largely abrogated (Galletti et al., Vaccine 13:197-201, 1995; Osterhaus et al., Vaccine 16:1479-81, 1998; Siegrist et al., Vaccine 16:1409-14, 1998; Siegrist et al., Dev. Biol. Stand. 95:133-9, 1998).
Replication-competent vaccinia recombinants expressing the protective antigens of RSV have also been shown to be ineffective in inducing a protective immune response when they are administered parenterally in the presence of passive antibody (Murphy et al., J. Virol. 62:3907-10, 1988a), but they readily protected such hosts when administered intranasally. Unfortunately, replication-competent vaccinia virus recombinants are not sufficiently attenuated for use in immunocompromised hosts such as persons with human immunodeficiency virus (HIV) infection (Fenner et al., World Health Organization, Geneva, 1988; Redfield et al., N. Engl. J. Med. 316:673-676, 1987), and their administration by the intranasal route even to immunocompetent individuals would be problematic. Therefore they are not being pursued as vectors for use in human infants, some of whom could be infected with HIV.
The MVA vector, which was derived by more than 500 passages in chick embryo cells (Mayr et al., Infection 3:6-14, 1975; Meyer et al., J. Gen. Virol. 72:1031-1038, 1991), has also been evaluated as a potential vaccine vector for the protective antigens of several paramyxoviruses (Durbin et al., J. Infect. Dis. 179:1345-51, 1999a; Wyatt et al., Vaccine 14:1451-1458, 1996). MVA is a highly attenuated host range mutant that replicates well in avian cells but not in most mammalian cells, including those obtained from monkeys and humans (Blanchard et al., J. Gen. Virol. 79:1159-1167, 1998; Carroll et al., Virology 238:198-211, 1997; Drexler et al., J. Gen. Virol. 79:347-352, 1998; Sutter et al., Proc. Natl. Acad. Sci. U.S.A. 89:10847-10851, 1992). Avipox vaccine vectors, which have a host range restriction similar to that of MVA, also have been constructed that express measles virus protective antigens (Taylor et al., Virology 187:321-8, 1992). MVA is non-pathogenic in immunocompromised hosts and has been administered to large numbers of humans without incident (Mayr et al., Zentralbl. Bakteriol. [B] 167:375-90, 1978; Stickle et al., Dtsch. Med. Wochenschr. 99:2386-92, 1974; Werner et al., Archives of Virology 64:247-256, 1980). Unfortunately, both the immunogenicity and efficacy of MVA expressing a paramyxovirus protective antigen were abrogated in passively-immunized rhesus monkeys whether delivered by a parenteral or a topical route (Durbin et al., Virology 235:323-332, 1999). The immunogenicity of DNA vaccines expressing measles virus protective antigens delivered parenterally was also decreased in passively-immunized hosts (Siegrist et al., Dev. Biol. Stand. 95:133-9, 1998). Replication-defective vectors expressing measles virus protective antigens are presently being evaluated, including adenovirus-measles virus HA recombinants (Fooks et al., J. Gen. Virol. 79:1027-31, 1998). In this context, MVA recombinants expressing parainfluenza virus antigens, unlike replication-competent vaccinia virus recombinants, lacked protective efficacy when given by a mucosal route to animals with passively-acquired antibodies, and it is unlikely that they, or the similar avipox vectors, can be used in infants with maternally-acquired measles virus antibodies. Based on these reports, it is not expected that poxvirus vectors or DNA vaccines expressing a measles virus protective antigens will be satisfactorily immunogenic or efficacious in infants that possess passively-acquired maternal measles virus-specific antibodies.
More recent developments in the field of negative stranded RNA viral vaccines have involved the use of HPIV3-based vaccine vectors to deliver antigenic determinants of heterologous pathogens, including heterologous PIVs. In particular, recombinant HPIV3 vaccine candidates have been disclosed that use a HPIV3 “vector” genome or antigenome combined with one or more heterologous genes of a different PIV, or of a non-PIV pathogen to form a chimeric, bivalent or multivalent, HPIV3 vaccine candidate (see, e.g., Durbin et al., Virology 235:323-332, 1997; Skiadopoulos et al., J. Virol. 72:1762-1768, 1998; Skiadopoulos et al., J. Virol. 73:1374-1381, 1999; Tao et al., Vaccine 19:3620-3631, 2001; Durbin et al., J. Virol. 74:6821-6831, 2000; U.S. patent application Ser. No. 09/083,793, filed May 22, 1998; U.S. patent application Ser. No. 09/458,813, filed Dec. 10, 1999; U.S. patent application Ser. No. 09/459,062, filed Dec. 10, 1999; U.S. Provisional Application No. 60/047,575, filed May 23, 1997 (corresponding to International Publication No. WO 98/53078), U.S. Provisional Application No. 60/059,385, filed Sep. 19, 1997; U.S. Provisional Application No. 60/170,195 filed Dec. 10, 1999; and U.S. patent application Ser. No. 09/733,692, filed Dec. 8, 2000 (corresponding to International Publication No. WO 01/42445A2), each incorporated herein by reference. The recombinant HPIV3 viruses are engineered to incorporate one or more heterologous donor sequences encoding one or more antigenic determinants of a different PIV or heterologous pathogen to produce an infectious, chimeric, bivalent or multivalent virus or subviral particle. In this manner, candidate HPIV3-based chimeric vaccine viruses can be made to elicit an immune response against one or more PIVs or a polyspecific response against a selected PIV and a non-PIV pathogen in a mammalian host susceptible to infection therefrom. Various modifications to chimeric HPIV3 vaccine candidates are reported to yield desired phenotypic effects, such as attenuation.
Although there have been numerous advances toward development of effective vaccine agents against PIV and other pathogens, including measles, there remains a clear need in the art for additional tools and methods to engineer safe and effective immunogenic compositions to alleviate the serious health problems attributable to these pathogens, particularly among young infants. Among the remaining challenges in this context is the need for additional tools to generate suitably attenuated, immunogenic and genetically HPIV1 candidates for use in diverse clinical settings against one or more pathogens. Additional challenges arise from the fact that HPIV1, HPIV2, and HPIV3 represent distinct viral serotypes, that do not elicit significant cross-protective immunity. Accordingly, there is an urgent need in the art for new immunogenic compositions and methods directed against multiple HPIV serotypes to treat, prevent, or alleviate the frequency or severity of the serious lower respiratory tract disease and the otitis media that accompanies different HPIV infections. To facilitate these goals, existing methods for identifying and incorporating attenuating mutations into recombinant viral strains and for developing vector-based immunogenic compositions and immunization methods must be expanded. In this context, it is particularly desirable to develop a method for recovery and genetic manipulation of HPIV1, to generate immunogenic compositions to elicit immune responses against this important human PIV, and to provide additional tools to generate novel vectors and immunization methods. Surprisingly, the present invention satisfies these needs and fulfills additional objects and advantages as described herein below.